GCN Circular 27818

S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed the detection of a long GRB 200524A, which was also detected by Fermi-LAT (Dirirsa F. et al., GCN #27797), Swift (Evans P.et al., GCN # 27798), ZTF (Ho A. et al., GCN # 27799), GROWTH-India (Kumar H. et al., GCN # 27800), Global MASTER-Net (Lipunov V. et al., GCN # 27801), CrAO (Rumyantsev V. et al., GCN # 27802), 3.6m DOT (Sanwal P. et al., GCN # 27803), Liverpool (Perley D. et al., GCN # 27805), CAHA (Postigo A. et al., GCN # 27807), Fermi GBM (Pookalil S. et al., GCN # 27809), OAJ (Blazek M. et al., GCN # 27810) and Swift-XRT (Capalbi M. et al., GCN # 27811).

The source was clearly detected in the 40-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-05-24 05:04:05.494 UT. The measured peak count rate associated with the burst is 303 +/- 22 cts/s above the background in the combined data of four quadrants, with a total of 2111 +/- 37 cts. The local mean background count rate was 537 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 15.38 +/- 0.27 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-05-24 05:04:04.236 UT. The measured peak count rate is 430 +/- 40 cts/s above the background in the combined Veto data of four quadrants, with a total of 2951 +/- 79 cts. The local mean background count rate was 1623 +/- 3 cts/s.  We measure a T90 of 16.89 +/- 0.67 s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.